1. Field of the Invention
This invention relates to a building material formed from a settable composition including landfill leachate.
2. Description of the Related Art
Coal combustion products (CCP) are the byproducts generated from burning coal in coal-fueled power plants. These CCP include fly ash, bottom ash, boiler slag, and flue gas desulfurization materials. Today, most coal combustion products are stored in monofill landfills that are lined, eventually covered, and constructed with leachate collection systems. Large volumes of CCP are landfilled annually because the supply of material exceeds demand in construction and miscellaneous other applications. There are also situations where the consistency of chemical or physical characteristics do not align with specification requirements for projects resulting in disposal. The American Coal Ash Association reported that over 131 million tons of CCP were produced in the USA during 2007. Approximately 40% of the CCP produced annually are beneficially used which leaves 60% destined for disposal.
One of the most proven and highly valued uses for CCPs are in the cement and concrete industry. For example, fly ash (as described in ASTM C 618) can be used as a cementitious and/or pozzolanic material (typically with Portland cement) in the production of concrete. Bottom ash is sometimes also used as an aggregate in concrete. Fly ash and bottom ash are commonly used as raw-feed materials in cement manufacturing as alternatives to conventional clay, shale or other mined minerals. Power plant flue gas desulfurization gypsum or mined gypsum are also used in cement manufacturing and interground with clinker as an important additive for helping to control the time-of-set of Portland cement products.
Still, significant amounts of coal combustion products are disposed in landfills. As water (from material stabilization, precipitation, dust control and compaction) percolates through the coal combustion products in a landfill, the water picks up chemicals and minerals. This water with chemicals and minerals is called leachate. Landfill leachate commonly has to be trucked or piped to a wastewater facility for treatment at a cost.
Fresh water is typically used for concrete and related building materials production. However, fresh water is a limited and valuable natural resource.
Thus, there is a need for a safe and economically advantageous means for avoiding wastewater treatment of landfill leachate. Also, there is a need for a means for conserving fresh water that is normally used in the production of building materials such as concrete.